1. Field of the Invention
The present invention relates to a junction block for branching away and connecting together wires which form a wire harness.
2. Description of Prior Art
A junction block as shown in FIG. 6 have been conventionally used for branching away and connecting together wires which form a wire harness. With this type of junction blocks, bus bars 2, 2', 2" are sandwiched between an upper case 1 and a lower case 4. Each of the bus bars is stacked in multi-layers with insulating substrates 3, 3' . . . inserted therebetween, having a plurality of electrically conductive tabs (male contacts) 2a, 2a', 2a". The tabs 2a, 2a', 2a" protrude into a connector-receiving portion 5, formed on the upper case 1 or on the lower case 4, for electrical connection with external wires or circuits through a connector, which is to be inserted into the portion 5. A relay terminal 6 is a female-female type relay terminal for connecting conductors through U-links as shown in FIG. 9.
FIG. 7 illustrates an electrical equivalent circuit of the bus bars in the junction block described above, in which one circuit (bus bar) is used for providing four tabs a, b, c, and d.
In order to provide branch circuits and the tabs at predetermined positions on the junction block using the bus bars, it is necessary to allow the tabs 2a, 2a', to protrude upwardly or downwardly at different locations on the bus bars as shown in FIG. 6. However, arranging tabs on different bus bars into individual groups causes design problems such as difficulty in routing bus bars and interferences from other bus bars, leading to a long assembly time. In the mean time, Japanese Patent KOKAI publication No. 61-435575 discloses a technique of high density construction of a junction circuit as shown in FIG. 8. A group of specific wires 7 that branch away from a wire harness W are disposed in parallel to each other, and are sandwiched between an upper case 8 and a lower case 9. The wires 7 are pressed into slots 12 of friction contact portions 11 of friction contact terminals 10. Male type contacts 13 on the side opposite to the friction contact portions 11 protrude into female-connector receiving portions 14 formed on the upper case 8. Connectors 15 on which other wires 7' that branch away from the wire harness W are assembled, are inserted into the portions 14 of the upper case 8, thus electrically interconnecting the wires 7 and 7'.
However, this type of junction blocks suffer from disadvantages that the friction contact terminals 10 can be mounted only on one side of the upper case 12; therefore grouping up of the male contacts 13 is rather difficult because of limited locations of the portions 14 and the number thereof. Also, the wires from the wire harness W are directly assembled in the junction block; therefore the harness wire cannot be assembled independently of conductors in the junction block, causing complexity of assembly process.